1. Field of the Invention
The present invention relates to an electropneumatic regulator system which makes it possible to perform remote control of an electropneumatic regulator, for example, by using a master station installed in a serial communication network.
2. Description of the Related Art
In general, the electropneumatic regulator controls the pressure and the flow rate of a fluid supplied from a fluid source, in response to the level of an input signal (a voltage signal or a current signal). Volumetric remote control or connection to a control unit such as PC or a computer makes it possible to control the flow rate and the pneumatic pressure of various types of actuators. Therefore, the electropneumatic regulator is widely applicable, for example, to the control of application of force for press die cushions, the multispeed control for cylinders, the control of application of force for electrodes of welding machines, the control of rotation for air motors, and the control of application of force for low pressure casting machines.
The electropneumatic regulator is previously subjected to the initial setting before the start of use. The initial setting includes, for example, the zero adjustment and the span adjustment as shown in FIG. 11. The zero adjustment is performed to change a basic state in which the output pressure is 0% when the input signal is 0% in order to establish another state in which the output pressure is generated with an offset to some extent. The span adjustment is performed in order to adjust the slope of the input and the output.
During the ordinary use, the operation is performed such that a control unit (for example, a computer), which is exclusively equipped for the electropneumatic regulator, is used to output a pressure command signal to the electropneumatic regulator.
In order to realize, for example, the multifunctional operation for various types of systems based on the use of the electropneumatic regulator, a multi-stage electropneumatic regulator system is used, or a large number of electropneumatic regulators are dispersed over a large system in some cases.
In such a case, the following methods are conceived when the individual electropneumatic regulators are controlled by using exclusively equipped control units respectively. That is, operators are arranged at a plurality of points at which the control units are installed respectively, or an operator goes around the plurality of points to perform the control.
However, the former method involves a problem that the cost is extremely expensive, and such a method is not practical. The latter method involves a problem that it is impossible to perform the control in real time.